A Phase II, Multicenter, Randomized, Controlled Clinical Study Comparing the Efficacy and Safety of Sintilimab Plus SOX Versus SOX Alone as Adjuvant Therapy for PD-L1-Positive, Stage pN3 Gastric Cancer

This study is testing whether adding sintilimab (an immunotherapy drug that helps the immune system attack cancer) to standard chemotherapy after stomach cancer surgery can reduce the chance of the cancer coming back in patients with a specific high-risk cancer type. **You may be eligible if...** - You are between 18 and 75 years old - You have been diagnosed with gastric (stomach) adenocarcinoma - Your cancer was completely removed by surgery with extensive lymph node removal (D2 or wider resection, R0 status) - Your cancer was at pathological stage N3 (extensive lymph node involvement) without distant spread - Your tumor tests positive for PD-L1 (a marker predicting immunotherapy benefit, CPS ≥1) - You did not receive chemotherapy before surgery **You may NOT be eligible if...** - You received neoadjuvant (pre-surgery) chemotherapy - Your surgery did not achieve clear margins - Your cancer has spread to distant organs - You have autoimmune conditions or cannot tolerate immunotherapy Talk to your doctor to see if this trial is right for you.